Lead-in conductor for mercury vapor tubes



7 F. LAUST ER LEAD-IN CONDUCTOR FOR MERCURY VAPOR TUBES Jan. 23, 1940.

Filed Nov. 4, 1936 Patented Jan. 23, 1940 UNITED STATES PATENT OFFICELEAD-IN CONDUCTOR FOR MERCURY VAPOR TUBES In high pressure mercury vaportubes, as is known, the output of radiation increases as the specificload of the discharge is increased. An object of this invention is toprovide a lead-in s conductor for tubes adapted to carry high currentloads.

This high current load necessitates that all dead spaces which might actas condensation points for the mercury vapor be avoided. The

to familiar tungsten wire leads, which are fused into quartz by using asingle transition glass, avoid dead spaces but can only carry a lowcurrent load and are therefore unsuitable. In the present inventionmetal foils of less than 0.02 mm. thick- 16 ness are used as currentleads. Such toils can be fused directly into the quartz tube and cancarry current loads up to ten amperes. Thus a high order or radiationoutput is obtained with tubes made according to this invention and asatisfac- U tory operating life is achieved atthe same time owing to thecomparatively low vapor pressure developed.

with high pressure mercury vapor tubes there is a danger that part ofthe mercury required for 85 operation may condense in the pole chambers,where the temperature is considerably lower than in the remainder of thetube. To prevent such condensation, the wall thickness of the polechambers is made greater than that of the reso mainder of the tube,thereby increasing the temperature on the inner walls of the polechambers. As a further precaution the section of the tube available tothe arc may be constricted in the viclnity oiLthe pole chambers.

' In some cases the enlargement of the wall thickness may be limited bythe external or the internal diameter of the pole chambers. In thisevent, the pole chambers may be screened oi! from the remainder of thetube by means of flanges which will cause more electrical energ to beconverted into heat in the pole chambers. The provision of constrictionsand/or flanges as such is known. but these have hitherto been employedfor different reasons. It is only when tubes. ac-

cording to the invention. develop vapor pressures in excess or liveatmospheres that a constriction in the vicinity of the pole chamberswill produce any considerable increase in the potential gra-" dientswith the accompanying conversion into 50 heat within the pole chambers.

In the accompanying drawing, Fig. 1 is asomewhat diagrammaticlongitudinal sectional view of showing the lead-in foil. Fig. 3 is aperspective view of part of a lead-in foil and part 01 an electrodeconnected therewith. Fig. 4 is a perspective view similar to Fig. 3 of amodified embodiment of the leadein foil and electrode. The 5 tube Iconsists of quartz. The are tube portion 2 is screened off from the polechambers 5 and 6 by means of flanges 3 and 4. The thermionic electrodes1 and 8 can, for example, consist oi. tungsten wire wound round athicker timgsten wire, or other metals with high melting points may beused to advantage in some circumstances. Substances having a low workfunction, e. g. alkaline earth oxides, are applied to the electrodesinknown manner, the electrodes preferably being heated to the necessaryincandescence by the discharge itself. On the thick tun sten wiresarefastened metal toils 9 and I which are fused into quartz capillariesof suitable section to form a high vacuum-tight seal. In doing this, itis advanta eous to lay the ends of the tungsten wires in a fold oi thetoil so as to obtain a good electrical contact with the drawing in ofthe quartz. The i'nils are protected against the discharge it. as shownin the illustration. the ends of the pole chambers have an opening onlyexacti.v sumcient for the passage or the tungsten wires. The metalliclead in foils are made of a refractory metal such as tungsten ormolybdenum and. or a width of about 3 to mm., are of a thickness whichis less than 0.02 mm. and preferably less than 0.01 mm. Such thin foilscan be fused directly into the quartz. They form a completely vacuumtight seal, requiring no further sealing means. The outer current leadsmay not be connected directly to these foils since the latter are not orgreat mechanical strength and, moreover. are often damaged where theyare not embedded in quartz. by oxidation during operation. It is.therefore. necessary to attach a strong wire to 40 these foils and toconnect the external current leads thereto. As shown on the drawing,this is done by folding the foils over once and placing the wire betweenthe foils. The foils may be penetra ed at the folds so that theconnector wire is positioned axially, as shown by the drawing. Currentconnection to the electrodes is accomplished in similar manner. Theconnection between the tails andthewiremaybeeflectedby welding. ifdesired. In general, however, welding is not necessary. The fusing ofthe foils into the quartz must be carried out in vacuum. It is.therefore, convenient to place the foils and the folded-in connectorwires in a quartz tube having a suitable inside diameter and to evacuatethe interior thereof. Alter softening of the quartz, the quartz tube iscompletely pressed together bymeansoiexternalairpressuresothatitislndirect contact throughout with thefoil, includinz the folded parts. Upon cooling of the quartz, the rigidmaterial encom the toil prevents the connection from becoming loose.This joint is thus adequate even for large currents. To avoidcondensation of the mercury, the wall I! of the pole chambers 5 and i ismade thicker than the wall II o! the arc tube .2. Owing to the greaterfall of temperature within the walls or the pole chambers, even thesmaller transformation of electrical energy around the incandescentelsetrodes will produce sufllcient heating on the inner walls of thepole chambers. The eflect of this improvement is further enhanced by thescreening flanges 1 and 4. As a. result of these two measures,condensation of themercury inside the pole chambers is prevented. Theinternal diameter of the arc tube 2 is made as large as possible toensure that the arc is kept away from the walls of the arc tube, limitedhowever to a certain extent as otherwise the arc becomes unstable inoperation. It is also important to fix the dimensions of the arc tube sothat the coldest spot therein is maintained at such a temperature so asto produce a vapor pressure in excess otfive atmospheres. For instance1118!! Pressure mercury vapor tubes, according to the illustration haveproved satisfactory with an internal diameter of 8 mm., a wall thicknessor 1.5 mm. and a distance between electrodes of 40 mm., operating with avoltage drop of about 26 volts/cm. and a current load of 1.0 ampere. Thewattage is about 100 watt.

In some cases it is advantageous to use electrodes heated by externalmeans. In this event, a further fusion lead is required and this can beprovided by using two thin metal ioils of about equal thickness, one asthe lead-in for the current and the other for the heating of theelectrode.

What I claim is:

A lead-in conductor for conducting currents of up to 10 amperes to highpressure mercury vapor tubes made of quartz and having solid endportions comprising a strip metal foil having its ends folded back andwires connected to said foil by passing between the layers of the foldedbaclrends of the foil, the foil including at least a portion of thefolds embedded in quartz.

FRANZ LAUS'I'ER.

CERTIFICATE OF CORRECTION Patent No. 2,1 7, 60. January 25, 19mg.

- 'Fmnz IAUSTER.

It is herebylcertified that'error appears ip'the above m mbered patentrequiring cprrection as follows In' the heading tpthqprihtfedspecification,

' after line 5,- insert; in Germany Novemper' 15, 1935"; and that theand Letters Patent should be read, with this correction therein that theaam e may confom to the reord 0! F116. ca'se' in the fatal 1t .Offibe.

Signed. and sealed thia'lhth day- 0'! may, A. D. 1911.0.

--Henry Vain Ara dfile, (Seal) Acting Gomhiaaioner o; Ptents.

' after line 5, insert In Germany Novemper' 15, .1935",

CERTIFICATE OF CORRECTION:

' J m 2;. 19m;- rmuz IAUS'I'ER. 7 It is herebylcertified thaterrorappears ipthe abovo n'fimb requiring cprrection as foliowa In theheading tp-thqprihtfed specification, and that the sa id Patent No.2,187,860.

ered patent .Letters Patent should be read with tibia-correction thereinthat the 5am? may. confoim to the rebord of tgh'e case in the Paterit.Offi'ce."

Signed and sealed thia'lhth 1 0'! May, A. n. 191p.

Agting Gmm'niaasloneg' qr Ptexits.

